Abstract

The Putu 11 simulation model was used to simulate veld production for each of 47 years, using weather input data and soil properties of a site at Glen. Grassland drought was defined as that condition encountered when 100 kg/ha or less standing dry matter was simulated. Model simulations of monthly DM production at five selected stocking rates were used for determining the dates of occurrence and duration of the droughts. Simulated drought duration was found to be linearly related to stocking rate. Theoretically, no droughts were identified at stocking rates less than 6,25 ha/LSU. A simple economic analysis of the results indicated that the gross profits were optimised at a rate of 5,78 ha/LSU. The use of mathematical models for drought analysing and classification was successfully demonstrated.